Vicious Venues - The Maw
The Maw is a vicious deathtrap that makes use of loosely hanging stalagmites that drops down on the unwary who passes through the toothy maw of a cavernous grotto. It can be incorporated into any cave area that has a complicated rock formation whether on a sea cliff or underground.
There can be plenty of reasons why adventurers would be encountering this trap from treasure to undead to sinister cults but they are not going to expect something to be befalling on them.
This article features the Maw as a trap for 3 different encounter levels (3,5,8) each is simply an upgrade of the DCs it takes to notice or disarm the trap and the damage that the PCs take if they fail to dodge its attack. Any character that is hit by the Maw trap is also knocked prone and would have to crawl their way out while the crashing stalagmites effectively creates a blocked area for others to go through.
The main difference between the different encounter levels of this trap is the monsters that also occupy in the grotto. The trap is accompanied by two pairs of ranged and melee monsters. The ranged monsters are positioned in a fortified area raining bolts and blast on those who are safe from the trap. While the melee monsters attempt to keep those trapped to stay in.
This is one nasty trap but it is hard to visualize without a map.